@TP-Link Thanks for your prompt reply. Prior upgrading the firmware, when I reboot the Deco on Ground Floor, most of the time it will select the Signal Source pointing at 1St Floor Deco. However...

I've 3 Deco at home (3 storey house) and I am placing 1 Deco at each floor. My ISP modem router is located on 2nd floor which is the main Deco. Before upgrading to "1.5.1 Build 20210330 Rel. 64251"...